Modelling acute antibody-mediated rejection of human kidney transplants using ex-vivo warm machine perfusion.

BACKGROUND: Transplant rejection is a major cause of graft loss and morbidity. Currently, no human models of antibody-mediated rejection (AMR) exist, limiting mechanistic investigation and organ-specific targeted therapy. Here, using 12 human kidneys and ex-vivo normothermic machine perfusion, we demonstrate phenotypes of AMR after addition of antibodies against either human HLA class I or blood group antigens (A, B), thus modelling clinical AMR that can follow HLA incompatible (HLAi) or blood group incompatible (ABOi) transplantation. METHODS: Discarded human kidneys with wide ranging demographics and cold ischaemia times (11-54 h) were perfused with red blood cells and fresh frozen plasma (FFP) as a source of complement/coagulation factors. For the HLAi model, 600 µg of W6/32 anti-class 1 HLA antibody was added to the circuit (time '0'). For the ABOi model, high titre FFP of the relevant blood group antibody was added. Renal blood flow index (RBFi, mL/min/100 g), C3 desArg, prothrombin fragments 1 + 2 and histology were determined. Our endpoints included haemodynamic changes, thrombosis, and biopsy proven complement deposition. FINDINGS: Compared to control kidneys perfused without anti-donor antibodies, both models demonstrated haemodynamic collapse after antibody perfusion with only the HLAi model showing glomerular C4d deposition. INTERPRETATION: We show that a clinically relevant human kidney model of AMR is feasible, and anticipate that these models, with refinements, could provide a basis to test different strategies to prevent AMR. FUNDING: The Rosetrees and Stonygate Trust, The Royal College of Surgeons of England Fellowship Grant, NIHR Biomedical Research Centre/KCL Early Career Grant, Kidney Research U.K.

Streptococcus pneumoniae as a Cause of Mycotic and Infected Aneurysms in Patients without Respiratory Features: Challenging Diagnoses Aided by 16S PCR.

BACKGROUND: Streptococcus pneumoniae is considered a rare cause of mycotic aneurysms. The microbiological diagnosis of mycotic aneurysms can be difficult, and many patients have negative blood culture results. METHODS: We describe a series of four consecutive cases of mycotic aneurysms caused by S. pneumoniae with no respiratory features or extravascular septic foci. In two patients with negative blood culture results, 16S PCR was used for the diagnosis of S. pneumoniae infection. RESULTS: Four men with mycotic aneurysms affecting the aorta, axillary, and popliteal arteries caused by S. pneumoniae presented to our center between 2015 and 2016. All were treated with at least one month of intravenous antibiotics, followed by at least 4 weeks of oral antibiotics. Two were additionally managed using endovascular surgical techniques, and one underwent an open surgical repair. The fourth patient presented with bilateral popliteal aneurysms, one of which ruptured and was managed using surgical ligation and bypass, whereas the other side subsequently ruptured and was repaired endovascularly. Three of the four patients are currently off antibiotics and considered cured, while one died of an unrelated cause. CONCLUSIONS: S. pneumoniae should be considered a potential causative agent of mycotic aneurysms. Diagnosis can be confirmed using 16S PCR, especially in patients where peripheral blood cultures are uninformative.

Clinical-pathological correlations in post-transplant thrombotic microangiopathy.

AIMS: Post-transplant thrombotic microangiopathy (TMA) is a rare and clinically challenging finding in renal transplant biopsies. In addition to recurrent atypical haemolytic uraemic syndrome, TMA in renal transplants is associated with various conditions, such as calcineurin inhibitor (CNI) treatment, antibody-mediated rejection (ABMR), viral infections, sepsis, pregnancy, malignancies, and surgery. The therapeutic implications of this diagnosis are considerable. In order to better understand post-transplant TMA and to identify histological or clinical differences between associated causes, we conducted a multicentre retrospective study. METHODS AND RESULTS: Clinical parameters and transplant renal biopsy findings from 81 patients with TMA were analysed. Biopsies from 38 patients were also analysed with electron microscopy. On the basis of clinical-pathological correlation, TMA was attributed to a main aetiology, whenever possible. TMA occurred at a median of 30 days post-transplantation. Systemic features of TMA were present in only 18% of cases. Twenty-two per cent of cases were attributed to CNI and 11% to ABMR. Although other potentially contributing factors were found in 56% of patients, in most cases (63%) no clearly attributable cause of TMA was identified. Histological differences between groups were minimal. The detection of ultrastructural features that are usually associated with ABMR may help to establish ABMR as the cause of TMA. CONCLUSIONS: Although CNI and ABMR appear to be the main contributors to post-transplant TMA, the aetiology of most cases is probably multifactorial, and TMA cannot be unequivocally attributed to a single underlying aetiology. Morphological features of TMA are not discriminating, but electron microscopy may help to identify ABMR-associated TMA.

Incidence and Outcome of C4d Staining With Tubulointerstitial Inflammation in Blood Group-incompatible Kidney Transplantation.

BACKGROUND: The last Banff 2013 report recognizes acute/active antibody-mediated rejection (ABMR) and C4d staining without evidence of rejection. The goal of our study was to analyze the incidence of C4d deposition after ABO-incompatible transplantation and assess outcomes in patients with ABMR, C4d staining without evidence of rejection (all acute Banff scores = 0), and C4d staining with tubulointerstitial inflammation (i > 0 with or without tubulitis). METHODS: Three-months 'For cause' or protocol biopsies in 50 ABO-incompatible patients were rescored and were correlated with clinical outcomes and antibody titres. RESULTS: Active/acute ABMR was found in 23 patients (46%), C4d staining without evidence of rejection in 7 patients (14%), C4d staining with tubulointerstitial inflammation in 6 patients (12%), tubulointerstitial inflammation in 6 patients (12%), and no evidence of rejection in 8 patients (16%). Patients with active/acute ABMR had a 3-month estimated glomerular filtration rate (median,: 43 mL/min) lower than patients with no evidence of rejection (median, 61 mL/min; P = 0.01). However, after 3 months, a progressively declining estimated glomerular filtration rate was observed more frequently in patients with C4d staining and tubulointerstitial inflammation when compared to patients with no evidence of rejection (100% vs 25%, P = 0.03). Finally, independently of C4d status, interstitial inflammation occurred more frequently in patients with a pretransplant ABO antibody titre higher than 16 and/or posttransplant ABO antibody increase. CONCLUSIONS: Whereas isolated C4d deposition and isolated interstitial inflammation appear to be benign lesions, C4d deposition in association with interstitial inflammation is the biopsy finding most strongly associated with the development of chronic graft dysfunction.

Difference in outcomes after antibody-mediated rejection between abo-incompatible and positive cross-match transplantations.

Graft survival seems to be worse in positive cross-match (HLAi) than in ABO-incompatible (ABOi) transplantation. However, it is not entirely clear why these differences exist. Sixty-nine ABOi, 27 HLAi and 10 combined ABOi+HLAi patients were included in this retrospective study, to determine whether the frequency, severity and the outcome of active antibody-mediated rejection (AMR) were different. Five-year death-censored graft survival was better in ABOi than in HLAi and ABOi+HLAi patients (99%, 69% and 64%, respectively, P = 0.0002). Features of AMR were found in 38%, 95% and 100% of ABOi, HLAi and ABOi+HLAi patients that had a biopsy, respectively (P = 0.0001 and P = 0.001). After active AMR, a declining eGFR and graft loss were observed more frequently in HLAi and HLAi+ABOi than in ABOi patients. The poorer prognosis after AMR in HLAi and ABOi+HLAi transplantations was not explained by a higher severity of histological lesions or by a less aggressive treatment. In conclusion, ABOi transplantation offers better results than HLAi transplantation, partly because AMR occurs less frequently but also because outcome after AMR is distinctly better. HLAi and combined ABOi+HLAi transplantations appear to have the same outcome, suggesting there is no synergistic effect between anti-A/B and anti-HLA antibodies.

The handling and sampling of radical prostatectomy specimens for reporting and research: the Oxford approach.

This article reviews previously described methods of fresh tissue sampling from radical prostatectomy specimens for research and describes a method used in Oxford which is simple, logical and cost effective. The method utilises a systematic zonal approach to tissue procurement in order to meet the increasing requirement for research samples with detailed morphological information such as zone of origin, tumour stage and Gleason grade. The described method involves punch biopsy sampling from a 4mm thick transverse slice cut 8mm superior to the apex. 9 biopsies are taken from each specimen in the following zonal distribution: Mid anterior, right lateral, right peripheral zone lateral, right peripheral zone mid, left peripheral zone mid, left peripheral zone lateral, left lateral, left transition zone and right transition zone. The method was validated by successfully sampling tumour in 7 out of 8 cases (88%). In 6 of the positive cases, tumour was present in more than 1 punch biopsy. The mean time from receipt of the specimen to completion of the biopsy freezing was 23.5 minutes. Tumour stage, zone and Gleason grade were determined for all positive biopsies. All cases were reported to RCPath guidelines with no compromising of margins. A logical systematic method of fresh tissue sampling from radical prostatectomy specimens is presented, which balances the need for accurate routine histopathological reporting with the requirement for increasingly complex research samples to be taken with attention to morphological details such as zone and stage.

Ectopic pancreas, intussusception, and a ruptured mesenteric band: an unusual association.

Although ectopic pancreas and intussusception are not unusual conditions, intussusception caused by ectopic pancreas is extremely rare. Its presence along with a ruptured congenital mesenteric vascular band raises the possibility of an anomaly of the vitelline vascular system. We report the case of a 26-year-old man presenting with acute abdominal pain, vomiting, and diarrhea. CT scan showed a large amount of free fluid in his abdomen and an ileo-ileal intussusception. At laparotomy he was found to have hemoperitoneum with a ruptured, actively bleeding congenital band attached to the ileal mesentery, which was ligated, with ileo-ileal intussusception that was resected. Histopathology showed ectopic pancreatic tissue as the lead point for the intussusception. It was likely to be a ruptured mesodiverticular band and along with other findings suggested a constellation of anomalies of the vitello-intestinal tract.